I did an informal survey of the young managers [in Google’s Associate Product Manager program] and asked each to guess if he or she would be working for Google in five years. Not a single one answered in the affirmative. When I reported this to Mayer, she was unruffled. Actually, she told me, it would be a positive thing, because Google DNA would be spread throughout Silicon Valley, to the benefit of all.

If Google had a goal of spreading its DNA through the industry, Marissa Mayer taking the helm at Yahoo was quite a milestone. Mayer joins Facebook COO Sheryl Sandberg COO and AOL CEO Tim Armstrong as the most prominent of a long list of executives, investors and entrepreneurs who have left the Googleverse to play in the larger tech world. Or perhaps said differently, who have left Google Inc. to play elsewhere in the larger Googleverse.

Google chronicler Steven Levy paints Mayer as the central figure in the keeping, spreading, and articulating of Google’s culture and values. While others obsessed over the technology and (to a lesser extent) the business, she obsessed over the people, principles, and culture. That includes the design principles that we associate with Google: simplicity, minimalism, speed, user-focus, and metric-driven decision making.

I haven’t seen an explanation of why Mayer thought spreading the Google DNA would help Google. I suspect she’s right, though. Google is the world’s most successful middle man. It sits in the center of a tremendous network. Its growth relies on others continuing to build their business models in ways that keep Google in the center.

There are also issues of loyalty, networks, and public opinion. It matters a great deal whether the people who leave Google want to destroy Google or to help it. The internet industry now contains a loose but powerful network of internet professionals who feel some allegiance to Google.

More importantly, there are now many powerful individuals who see the Googleverse through certain paradigms, and are committed to certain values and principles. Those values and principles coincide well with Google’s business interests. These principles support publishers creating fast web sites that create unique content that satisfies (Google’s) users. They favor free content, monetized by contextual text ads. They share Google’s views regarding the cultural and legal environment on issues including content ownership and distribution, privacy, anti-trust law, net neutrality (good) and search neutrality (bad).

Ex-Googlers are not working in concert. They’re not directed by some central leadership council. They’re not trying to support Google Inc. But by individually pursuing the values and principles they shared at Google, they are supporting the Google-centered universe.

Generally speaking, this is good. The Googleverse is a remarkable place where consumers can learn about almost anything instantaneously, where people can get their ideas out, and where many companies are doing good things and making money. It’s good for Google, good for ex-Googlers, good for other companies in the industry, and good for the consumers.

But is it good for Yahoo? That’s a question that Marissa Mayer must explicitly ask herself. She should ask this about each individual value and principle that she taught at Google.

Having articulated and given conscious thought to these principles gives her a big advantage over other executives in similar circumstances, who may be less aware of the implicit assumptions driving their thoughts and actions.

Here’s some unsolicited advice for Ms Mayer

Write down all the principles that drove you at Google. You can start with existing values documents. Actively consider not only how the principle relates to Yahoo, but whether or not the reverse is now true.

For example, Google declares that one of the things it “knows to be true” is “It’s best to do one thing really, really well.” What would the one thing be for Yahoo? How would the opposite apply? Are there two or three things that can be combined for strategic advantage?

“Democracy on the Web works.” Maybe. Can that work for Yahoo? What about the reverse? Is there an opening on the web for an authoritative destination site? The brand dissonance of an elitist site named Yahoo may be too great. But yesterday’s rebel is tomorrow’s establishment. Sometimes democracy on the web creates mediocrity and worse, as is sometimes true on Yahoo Answers.

Ethical values like “you can make money without doing evil” don’t require reevaluation. But rethink tactical implications like “we firmly believe that ads can provide useful information if, and only if, they are relevant to what you wish to find.” It’s curious to believe such things so firmly. Where did Google get this firm belief? Is it possible that an ad can provide useful information even if it doesn’t relate to something you’re currently seeking? Is it possible that there are circumstances where it makes sense to run an ad that doesn’t provide useful information. These are the kinds of limiting beliefs you should consciously reevaluate.

Talk to other exGooglers. What struck them most when joining a new company? What parts of their worldview changed? Learning their lessons can give you a headstart and critical insights.

I’m hesitant to raise my last point. It’s none of my business, but none of this is. Many understandably find it offensive when a man gives a woman personal advice. I’ll do it anyway. Take care of yourself, Marissa. One of the many implicit values I ask you to question is that young professionals should work hundred hour weeks. Maybe that’s still right for you. Or maybe you can remain the image of professional commitment, intensity, joy, and fulfillment without, you know, killing yourself.